Errors With Xbit Mod, Need Help!

I've got a feeling this is going to be a bit long winded but please bear with me as I want to make sure I give as much info as possible in one post...

I had my XBox modded by a local company a few years back who have since disappeared. I think I have an XBIT mod. I have a panel on the back of my xbox with 4 jumpers, USB port and red & yellow connectors going to it (can upload a photo if required).

Basically my xbox stopped working giving me error code 16 if I just switch on and error code 05 if I put in a genuine xbox game (e.g Hitman 2).

Correct me if I'm wrong but from what I've read so far I need to discover which version of the chip I have, so my first question is since it's not booting up how do I do this?

Secondly when this originally happened I tried changing around the jumpers on the panel on the back of the XBox and now since some time has passed I can't remember which need to be on / off?

Final question, how do I fix it once I have the above info?

Sorry I know this probably seems a bit long winded etc. but I've been googling all day and gradually finding out bits and pieces and this looked the best resource for some answers.